Abstract: The dopaminergic (DA) synapse has been studied since the 1950s, when it was implicated in motor function, actions of antipsychotic drugs, and drug abuse. The study of DA synapses has however lagged behind that of other synapses, due to a lack of means to record dopamine release. To address this, chemical techniques have been developed, in particular electrochemical recording techniques and fluorescent false neurotransmitters (FFNs), that provide the first optical measure of neurotransmitter release from individual presynaptic sites. From these techniques, in some ways, we now know more about DA synapses than any other in the CNS. Here, we extend the contemporary understanding of DA synapses to reveal their roles in the interaction of higher organisms with the environment. This is now possible due to technical and conceptual advances, including the use of techniques novel to this proposal, including FFNs and DA-specific voltage sensors. This project tests if a) an interaction between sensory-related and reward-related excitation ?gates? local DA release, and whether this is required for normal learning and behavior; b) DA filters excitation by specific interactions with cannabinoid receptors to mediate decision-making and learning, c) learned behaviors that become established ?refine? synaptic circuits by selectively decreasing local DA activity, and that this enables future learning. The results of these experiments promise to indicate how addictive drugs such as amphetamine and opiates act to disrupt the normal operation of these steps.